CH4 Oxidation In Soils Research Articles

A simulation model for methane emissions from landfills with interaction of vegetation and cover soil

Global climate change and ecological problems brought about by greenhouse gas effect have become a severe threat to humanity in the 21st century. Vegetation plays an important role in methane (CH4) transport, oxidation and emissions from municipal solid waste (MSW) landfills as it modifies the physical and chemical properties of the cover soil, and transports CH4 to the atmosphere directly via their conduits, which are mainly aerenchymatous structures. In this study, a novel 2-D simulation CH4 emission model was established, based on an interactive mechanism of cover soil and vegetation, to model CH4 transport, oxidation and emissions in landfill cover soil. Results of the simulation model showed that the distribution of CH4 concentration and emission fluxes displayed a significant difference between vegetated and non-vegetated areas. CH4 emission flux was 1–2 orders of magnitude higher than bare areas in simulation conditions. Vegetation play a negative role in CH4 emissions from landfill cover soil due to the strong CH4 transport capacity even though vegetation also promotes CH4 oxidation via changing properties of cover soil and emitting O2 via root system. The model will be proposed to allow decision makers to reconsider the actual CH4 emission from vegetated and non-vegetated covered landfills.

Dynamics of soil-derived greenhouse gas emissions from shelterbelts under elevated soil moisture conditions in a semi-arid prairie environment

Soil moisture is known to be a major control of greenhouse gas (GHG) emissions from agricultural soils. However, there is little data regarding GHG exchange from the organic matter-rich soils characteristic of shelterbelts—especially under elevated soil moisture conditions. In the present study, we quantified CO2, CH4 and N2O fluxes from shelterbelts under elevated soil moisture (irrigated) and semi-arid (rainfed) conditions. Studies were carried out at the Canada-Saskatchewan Irrigation Diversification Centre (CSIDC) near Outlook, Saskatchewan. Non-steady state vented chambers were used to monitor soil GHG fluxes from three shelterbelts in 2013 and 2014. The shelterbelts consisted of a single row of caragana with a north–south orientation and a single row of Scots pine with either a north–south or east–west orientation. Each shelterbelt was divided into two areas based on whether or not it received irrigation. During the 2-year study period, N2O emissions from the irrigated shelterbelts (IR-SB) (0.93 kg N2O-N ha−1) were significantly greater than those from the rainfed shelterbelts (RF-SB) (0.49 kg N2O-N ha−1). Soil CH4 oxidation was significantly lower in the IR-SB compared to the RF-SB (−0.85 and −1.20 kg CH4-C ha−1, respectively). Irrigation activities stimulated CO2 production/emission in 2014, but had no effect on CO2 emissions during the much drier 2013 season. Correlation analyses indicate a strong dependence of CO2 and CH4 fluxes on soil moisture in both IR-SB and RF-SB sites. There was a significant relationship between N2O emissions and soil moisture for the IR-SB sites in 2013; however, no such relationship was observed in either the IR-SB or RF-SB sites in 2014. Our study suggests that changes in precipitation patterns and soil moisture regime due to climate change could affect soil-atmosphere exchange of GHGs in shelterbelts; however, elevated soil moisture effect on GHG emissions will depend on the availability of N and C in the shelterbelts.

Real-time monitoring of methane oxidation in a simulated landfill cover soil and MiSeq pyrosequencing analysis of the related bacterial community structure

Real-time CH4 oxidation in a landfill cover soil was studied using automated gas sampling that determined biogas (CH4 and CO2) and O2 concentrations at various depths in a simulated landfill cover soil (SLCS) column reactor. The real-time monitoring system obtained more than 10,000 biogas (CH4 and CO2) and O2 data points covering 32 steady states of CH4 oxidation with 32 different CH4 fluxes (0.2–125mol·m−2·d−1). The kinetics of CH4 oxidation at different depths (0–20cm, 20–40cm, and 40–60cm) of SLCS were well fit by a CH4-O2 dual-substrate model based on 32 values (averaged, n=5–15) of equilibrated CH4 concentrations. The quality of the fit (R2 ranged from 0.90 to 0.96) was higher than those reported in previous studies, which suggests that real time monitoring is beneficial for CH4 oxidation simulations. MiSeq pyrosequencing indicated that CH4 flux events changed the bacterial community structure (e.g., increased the abundance of Bacteroidetes and Methanotrophs) and resulted in a relative increase in the amount of type I methanotrophs (Methylobacter and Methylococcales) and a decrease in the amount of type II methanotrophs (Methylocystis).

Influence of methane and trichloroethylene domestication on bacterial community structure in landfill cover soil.

The biological oxidation capacity and change of microbial community structure of typical landfill cover soil cultured in situ by methane and trichloroethylene (TCE) were studied. The rates of CH4 oxidation and TCE degradation were 0.20-0.87 Μmol·g-1 soil·h-1 and 0.009-0.013 mg·L-1·h-1 among these landfill cover soils, respectively. The activity of CH4 oxidation in Shandong landfill cover soil was higher than that in landfill cover soils sampled from Guangdong, Shanghai and Chongqing. The α-diversity and microbial community structure before and after co-metabolism degradation were then investigated in all landfill cover soils by Illumina MiSeq sequencing. The results indicated that bacterial Operational Taxonomic Units (OTUs) were assigned to 39 phyla, 85 classes and 562 genera in all the commented OTUs clustering. The dominant bacterial populations were Proteobacteria, Bacteroidetes, Chloroflexi and Acidobacteria and the sum of the proportion was over 77.4% in all landfill cover soils. In addition, total percent of γ-Protebacteria, β--Protebacteria, α-Proteobacteria, Actinobacteria and Acidobacteria was over 26.5%. Specifically, the relative abundances of Methylophilaceae_uncultured, Anaerolineaceae_uncultured, Arthrobacter and Pseudomonas increased obviously after acclimated by TCE. These results suggested that there were co-metabolism degradation with non-methane compounds and aerobic assimilation of TCE besides the widely-agreed co-metabolism degradation by methanotrophs.

Stimulation of methane oxidation by CH4-emitting rose chafer larvae in well-aerated grassland soil

In this study, the impact of rose chafer (Cetonia aurata L.) larvae on net and gross methane (CH4) fluxes in soil from an old permanent grassland site (Giessen, Germany) was investigated. Previous studies at this site suggested the existence of Scarabaeidae larvae-induced “CH4-emitting hot spots” within the soil profile which may subsequently lead to increased CH4 oxidation. The net (soil + larvae) and gross (soil and larvae separated) CH4 fluxes were studied in a 3-month laboratory incubation. Addition of larvae changed the soil from a net sink (−330 ± 11 ng CH4 kg−1 h−1) to a net source (637 ± 205 ng CH4 kg−1 h−1). Supply of plant litter to the soil + larvae incubation jars tended to increase CH4 emissions which was not significant due to large variability. After 11–13 weeks of incubation, the net soil CH4 oxidation was significantly stimulated by 13–21% in the treatments containing larvae when these were taken out. Analysis of archaeal 16S rRNA genes revealed that the majority of the obtained clones were closely related to uncultured methanogens from guts of insects and other animals. Other sequences were relative to cultivated species of Methanobrevibacter, Methanoculleus, and Methanosarcina. Hence, Scarabaeidae larvae in soils (i) may represent an underestimated source of CH4 emissions in aerobic upland soils, (ii) may stimulate gross CH4 consumption in their direct soil environment, and, thus, (iii) contribute to the spatial heterogeneity often observed in the field with closed-chamber measurements. Long-term CH4-flux balances may be wrongly assessed when “exceptional” net CH4 flux rates (due to larvae hot spots) are excluded from data sets.

Greenhouse gas emissions along a shelterbelt-cropped field transect

The influence of shelterbelts on soil properties and crop yield at various distances from the shelterbelt have been studied; however, there are no available data detailing the spatial effects from shelterbelts into adjacent cropped fields on soil-derived greenhouse gas (GHG) emissions. The objective of this study was to quantify, for the first time, changes in soil CO2, CH4 and N2O fluxes along replicate (n=5) transects extending from the center of the shelterbelt to the center of the adjacent agricultural field. The shelterbelt was a 31-year-old, two-row hybrid poplar-caragana shelterbelt located in the parkland region of Saskatchewan Canada. Soil-derived GHG fluxes were measured using non-steady-state vented chambers placed along parallel transects situated within the shelterbelt strip (0H), at the shelterbelt edge (0.2H), at the edge of the adjacent cropped field (0.5H), and in the cropped field at distances of 40m (1.5H) and 125m (5H) from the shelterbelt. Summed over the entire study period, cumulative CO2 emissions were greatest at 0H (8032±502kg CO2-C ha−1) and lowest at 5H (3348±329kg CO2-C ha−1); however, the decrease in CO2 emissions at increasing distances away from the shelterbelt was irregular, with soil temperature and organic carbon distribution being the dominant controls. Soil CH4 oxidation was greatest at 0H (−1447±216g CH4-C ha−1), but decreased as distance from the shelterbelt increased. Conversely, soil N2O emissions were lowest at 0H (345±15gN2O-Nha−1) but increased with increasing distance from the shelterbelt. Patterns of soil CH4 uptake and N2O emissions were strongly correlated with root biomass, and soil temperature and moisture in the upper 30cm of the soil profile. Tree root distribution may be a key factor in determining the spatial range of shelterbelt effect on GHG emissions in adjacent fields

A mass balance model to estimate the rate of composting, methane oxidation and anaerobic digestion in soil covers and shallow waste layers

Although CH4 oxidation in landfill soil covers is widely studied, the extent of composting and CH4 oxidation in underlying waste layers has been speculated but not measured. The objective of this study was to develop and validate a mass balance model to estimate the simultaneous rates of anaerobic digestion (rAD), CH4 oxidation (rOX) and composting (rCOM) in environments where O2 penetration is variable and zones of aerobic and anaerobic activity are intermingled. The modelled domain could include, as an example, a soil cover and the underlying shallow waste to a nominated depth. The proposed model was demonstrated on a blend of biogas from three separate known sources of gas representing the three reaction processes: (i) a bottle of laboratory grade 50:50% CH4:CO2 gas representing anaerobic digestion biogas; (ii) an aerated 250mL bottle containing food waste that represented composting activity; and (iii) an aerated 250mL bottle containing non-degradable graphite granules inoculated with methanotrophs and incubated with CH4 and O2 to represent methanotrophic activity. CO2, CH4, O2 and the stable isotope 13C-CO2 were chosen as the components for the mass balance model. The three reaction rates, r (=rAD, rOX, rCOM) were calculated as fitting parameters to the overdetermined set of 4mass balance equations with the net flux of these components from the bottles q (=qCH4, qCO2, qO2 and qCO2×δ13C-CO2) as inputs to the model. The coefficient of determination (r2) for observed versus modelled values of r were 1.00, 0.97, 0.98 when the stoichiometry of each reaction was based on gas yields measured in the individual bottles and q was calculated by summing yields from the three bottles. r2 deteriorated to 0.95, 0.96, 0.87 when using an average stoichiometry from 11 incubations of each of the composting and methane oxidation processes. The significant deterioration in the estimation of rCOM showed that this output is highly sensitive to the evaluated stoichiometry coefficients for the reactions. r2 deteriorated further to 0.86, 0.77, 0.74 when using the average stoichiometry and experimental measurement of the composition and volume of the blended biogas to determine q. This was primarily attributed to average errors of 8%, 7%, 11% and 14% in the measurement of qCH4, qCO2, qO2 and qCO2×δ13C-CO2 relative to the measurement of the same quantities from the individual bottles.

Methane oxidation in response to iron reduction-oxidation metabolism in tropical soils

Experiments were carried out to understand how iron (Fe) reduction-oxidation (IRO) influences CH4 oxidation in soil. Soil samples (alluvial and vertisol) were induced to undergo microbial Fe reduction and aerobic oxidation consecutively for three cycles simulating natural wetting-drying soil cycle. After each IRO cycle, soils were incubated to determine CH4 oxidation rate, Fe mineral and methanotrophs abundance. Potential iron reduction rate k (μM Fe2+ produced g−1 soil d−1) increased from 1.26 to 2.16 in vertisol and 1.95 to 3.05 in alluvial soil. Potential iron oxidation (μM Fe2+ oxidized g−1 soil d−1) increased from 2.33 to 5.70 in vertisol and 2.43 to 9.58 in alluvial soil. The iron reduction-oxidation significantly (p < 0.05) stimulated CH4 oxidation rate k. The high affinity CH4 oxidation rate increased from 0.03 to 0.19. Low affinity CH4 oxidation rate increased from 0.05 to 0.47 in vertisol. A similar effect of IRO on k was observed in alluvial soil. X ray diffraction (XRD) revealed that diffraction intensity of magnetite and goethite decreased over IRO cycle. Real time PCR quantification of methanotrophs (pmoA gene) confirmed that IRO cycle stimulated (p < 0.05) methanotrophs abundance. The study highlights that iron reduction-oxidation cycles can significantly enhance CH4 oxidation in tropical soils.

Effects of preconditioning the rhizosphere of different plant species on biotic methane oxidation kinetics

The rhizosphere is known as the most active biogeochemical layer of the soil. Therefore, it could be a beneficial environment for biotic methane oxidation. The aim of this study was to document - by means of batch incubation tests - the kinetics of CH4 oxidation in rhizosphere soils that were previously exposed to methane. Soils from three pre-exposure to CH4 zones were sampled: the never-before pre-exposed (NEX), the moderately pre-exposed (MEX) and the very pre-exposed (VEX). For each pre-exposure zone, the rhizosphere of several plant species was collected, pre-incubated, placed in glass vials and submitted to CH4 concentrations varying from 0.5% to 10%. The time to the beginning of CH4 consumption and the CH4 oxidation rate were recorded. The results showed that the fastest CH4 consumption occurred for the very pre-exposed rhizosphere. Specifically, a statistically significant difference in CH4 oxidation half-life was found between the rhizosphere of the VEX vegetated with a mixture of different plants and the NEX vegetated with ryegrass. This difference was attributed to the combined effect of the preconditioning level and plant species as well as to the organic matter content. Regardless of the preconditioning level, the oxidation rate values obtained in this study were comparable to those reported in the reviewed literature for mature compost.

Soil–atmosphere exchange of carbon dioxide, methane and nitrous oxide in shelterbelts compared with adjacent cropped fields

Farm shelterbelts are used as a management tool to reduce erosion, conserve moisture, protect crops and buildings, and sequester carbon. Although carbon storage in shelterbelts has been well researched, there have been no measurements of soil trace gas exchange in shelterbelts relative to cropped fields. Our objective was to quantify, for the first time, soil CO2, CH4 and N2O fluxes from shelterbelts and compare them to emissions from adjacent cropped fields to assess their potential for greenhouse gas (GHG) mitigation. During 2013 and 2014, non-steady state vented chambers were used to monitor soil GHG fluxes from nine shelterbelts and their associated cropped fields at three locations within the Boreal plains and Prairies Eco-zones of Saskatchewan Canada. Mean cumulative CO2 emissions from shelterbelt soils were significantly (P<0.0001) greater than those from cropped fields (i.e., 4.1 and 2.1Mg CO2-Cha−1yr−1, respectively). However, soil organic carbon (SOC) storage (0–30cm) was 27% greater – representing an increase of 28Mgha−1 – in the shelterbelts than in the cropped fields. Soil CH4 oxidation was greater (P<0.0001) in shelterbelts than in adjacent cropped fields (i.e., −0.66 and −0.19kgCH4-Cha−1yr−1, respectively) and cropped soils emitted significantly (P<0.0001) greater quantities of N2O than the shelterbelts (i.e., 2.5 and 0.65kgN2O-Nha−1yr−1, respectively). Total seasonal exchange of non-CO2 GHGs was reduced by 0.55MgCO2eha−1yr−1 in shelterbelts as compared with cropped fields, 98% of which was soil-derived N2O. Patterns of soil temperature, moisture and organic matter distribution beneath shelterbelts suggest a modification in soil micro-environment due to shelterbelt establishment and root activity that, in turn, may be responsible for the observed increase in soil CO2 emissions and CH4 oxidation. Our data demonstrate that shelterbelts have substantial potential to mitigate GHGs by enhancing C storage and reducing N2O emissions, while maintaining a strong CH4 sink.

Effect of rice panicle size on paddy field CH4 emissions

Developing large rice (Oryza sativa L.) panicles has been widely regarded as an effective approach to increasing rice yield. However, it is unclear whether panicle size affects CH4 emissions from rice fields, especially during the reproductive stage. Here, we conducted two experiments (rice variety and mutant) to examine the effects of rice panicle size on CH4 emissions. The variety experiment under field conditions at two sites showed that rice yield was significantly and positively correlated with the spikelet number. Mean CH4 emissions during the reproductive stage were significantly and negatively correlated with spikelet number. The rice mutant experiment under pot and field conditions using a wild-type rice variety (WT) and its mutant (Mutant) demonstrated that CH4 emissions were significantly lower in the former with large panicles than in the later with small panicles, during the reproductive and grain filling stages (P < 0.01), whereas the rice yields showed an opposite. Root exudates and soil dissolved organic C concentration were significantly lower under the WT than under the Mutant. Soil CH4 production potential and mcrA gene copy number of the soil under Mutant were significantly higher than those of the soil under WT. There was no significant difference in soil CH4 oxidation potential and pmoA gene copy number between soils of these two rice varieties. Our results suggest that developing large panicles would benefit rice production for high yield with low CH4 emission.

Soil Methane Sink Capacity Response to a Long-Term Wildfire Chronosequence in Northern Sweden.

Boreal forests occupy nearly one fifth of the terrestrial land surface and are recognised as globally important regulators of carbon (C) cycling and greenhouse gas emissions. Carbon sequestration processes in these forests include assimilation of CO2 into biomass and subsequently into soil organic matter, and soil microbial oxidation of methane (CH4). In this study we explored how ecosystem retrogression, which drives vegetation change, regulates the important process of soil CH4 oxidation in boreal forests. We measured soil CH4 oxidation processes on a group of 30 forested islands in northern Sweden differing greatly in fire history, and collectively representing a retrogressive chronosequence, spanning 5000 years. Across these islands the build-up of soil organic matter was observed to increase with time since fire disturbance, with a significant correlation between greater humus depth and increased net soil CH4 oxidation rates. We suggest that this increase in net CH4 oxidation rates, in the absence of disturbance, results as deeper humus stores accumulate and provide niches for methanotrophs to thrive. By using this gradient we have discovered important regulatory controls on the stability of soil CH4 oxidation processes that could not have not been explored through shorter-term experiments. Our findings indicate that in the absence of human interventions such as fire suppression, and with increased wildfire frequency, the globally important boreal CH4 sink could be diminished.

Beyond nitrogen: The importance of phosphorus for CH4 oxidation in soils and sediments

Wetlands, lakes and agricultural soils are important sources and sinks of the greenhouse gas methane. The only known methane sink of biological nature is the oxidation by methanotrophic microorganisms, these organisms therefore provide an important ecosystem service. To protect this ecosystem service, it is important to maintain methanotrophic microorganism diversity, especially under increased anthropogenically-induced environmental pressures, such as imbalanced input of nutrients to ecosystems. There is therefore an urgent need to understand how N and P affect the structure and activity of methane oxidizing communities. Numerous research studies have already shown variable effects of N-addition on methane oxidation: small additions tend to stimulate methane oxidation, whereas large additions are inhibitory. There is however still a large knowledge gap concerning effects of P on methane oxidation. Here, we present data on the relation between methane oxidation and various measures of P in 50 drainage ditches, and summarize literature reporting relations between P and methane oxidation in wetlands and soils. Additionally, we review experiments on effects of P, N and N+P addition on both low affinity and high affinity methane oxidation. In our set of drainage ditches, as well as studies on wetland and permafrost soils, P content is positively correlated to methane oxidation, though it also co-correlates with many other variables. However, results from P-additions in rice paddies, agricultural soils, landfills, peat bogs, permafrost soils and forests were more variable: sometimes inhibiting (2 studies), other times stimulating methane oxidation (4 studies), and sometimes showing no effect (5 studies). Two studies report increased methanotroph (pmoA) abundance following P-fertilization, but little is known about effects of P on methanotroph community structure and its consequences for methane consumption. By mining methanotrophic genomes for genes involved in N and P-related processes, we demonstrate that variability in N/P related traits (influencing acquisition, uptake and metabolism) does not reflect DNA-based phylogeny. This review points to a need for better mechanistic understanding of the effects of P on methane oxidation, and the role of traits of methanotrophic community members in regulating this process.

Performance of green waste biocovers for enhancing methane oxidation

Green waste aged 2 and 24months, labeled “fresh” and “aged” green waste, respectively, were placed in biocover test cells and evaluated for their ability to oxidize methane (CH4) under high landfill gas loading over a 15-month testing period. These materials are less costly to produce than green waste compost, yet satisfied recommended respiration requirements for landfill compost covers. In field tests employing a novel gas tracer to correct for leakage, both green wastes oxidized CH4 at high rates during the first few months of operation – 140 and 200g/m2/day for aged and fresh green waste, respectively. Biocover performance degraded during the winter and spring, with significant CH4 generated from anaerobic regions in the 60–80cm thick biocovers. Concurrently, CH4 oxidation rates decreased. Two previously developed empirical models for moisture and temperature dependency of CH4 oxidation in soils were used to test their applicability to green waste. Models accounted for 68% and 79% of the observed seasonal variations in CH4 oxidation rates for aged green waste. Neither model could describe similar seasonal changes for the less stable fresh green waste. This is the first field application and evaluation of these empirical models using media with high organic matter. Given the difficulty of preventing undesired CH4 generation, green waste may not be a viable biocover material for many climates and landfill conditions.

The differential effects of ammonium and nitrate on methanotrophs in rice field soil

It has been known that nitrogenous fertilizers can either stimulate or inhibit methane oxidation in soils. The mechanism, however, remains unclear. Here we conducted laboratory incubation experiments to evaluate the effects of ammonium versus nitrate amendment on CH4 oxidation in a rice field soil. The results showed that both N forms stimulated CH4 oxidation. But nitrate stimulated CH4 oxidation to a greater extent than ammonium per unit N base. The 16S rRNA genes and the pmoA genes were analyzed to determine the dynamics of total bacterial and methanotrophic populations, respectively. The methanotrophic community consisted of type I and type II methanotrophs and was dominated by type I group after two weeks of incubation. Nitrate promoted both types of methanotrophs, but ammonium promoted only type I. DNA-based stable isotope probing confirmed that ammonium stimulated the incorporation of 13CH4 into type I methanotrophs but not type II, while nitrate caused almost homogenous distribution of 13CH4 in type I and type II methanotrophs. Our study suggests that nitrate can promote CH4 oxidation more significantly than ammonium and is probably a better N source for both types of methanotrophs in rice field soil. More investigations, e.g. using 15N labeling, are necessary to elucidate this possibility.

施氮对桉树人工林生长季土壤温室气体通量的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 施氮对桉树人工林生长季土壤温室气体通量的影响 DOI: 10.5846/stxb201401120086 作者: 作者单位: 中国科学院生态环境研究中心城市与区域生态国家重点实验室;中国科学院大学,中国科学院生态环境研究中心城市与区域生态国家重点实验室,中国科学院生态环境研究中心城市与区域生态国家重点实验室,中国科学院生态环境研究中心城市与区域生态国家重点实验室,中国科学院生态环境研究中心城市与区域生态国家重点实验室;河北师范大学生命科学学院,中国科学院生态环境研究中心城市与区域生态国家重点实验室,中国科学院生态环境研究中心城市与区域生态国家重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(31170425);中国科学院知识创新工程重要方向项目(KZCX2-EW-QN406);中国科学院战略性先导科技专项子课题(XDA05060102) Effects of nitrogen application on soil greenhouse gas fluxes in a Eucalyptus plantation during the growing season Author: Affiliation: State Key Laboratory of Urban and Regional Ecology,Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences;University of Chinese Academy of Sciences,State Key Laboratory of Urban and Regional Ecology,Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences,State Key Laboratory of Urban and Regional Ecology,Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences,State Key Laboratory of Urban and Regional Ecology,Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences,State Key Laboratory of Urban and Regional Ecology,Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences;College of Life Science, Hebei Normal University, Shijiazhuang,State Key Laboratory of Urban and Regional Ecology,Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences,State Key Laboratory of Urban and Regional Ecology,Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:施肥是维持短期轮伐人工林生产量的重要手段,为了提高肥料利用效率,缓释氮肥逐渐成为广泛采用的氮肥种类。评估缓释肥施用对人工林生长季土壤温室气体通量的影响对于全面评估人工林施肥的环境效应具有重要意义。以我国南方广泛种植的桉树林为对象,采用野外控制实验研究了4种施氮处理(对照CK:0 kg/hm2;低氮L:84.2 kg/hm2;中氮M:166.8 kg/hm2;高氮H:333.7 kg/hm2)对土壤-大气界面3种温室气体(CO2、N2O和CH4)通量的影响,结果表明:(1)4种施氮水平下CO2排放通量、N2O排放通量和CH4吸收通量分别为276.84-342.84 mg m-2 h-1、17.64-375.34 μg m-2 h-1和29.65-39.70 μg m-2 h-1;施氮显著促进了N2O的排放(P <0.01),高氮处理显著增加CO2排放和显著减少CH4吸收(P <0.05),且CO2排放通量与CH4吸收通量随着施氮量的增加分别呈现增加和减少的趋势;(2)生长季CO2和N2O排放呈现显著正相关(P <0.01),CO2排放和CH4吸收呈现显著负相关(P <0.05),N2O排放和CH4吸收呈现显著负相关(P <0.01);(3)土壤温度和土壤水分是影响CO2、N2O排放通量和CH4吸收通量的主要环境因素。结果表明:施用缓释肥显著增加了桉树林生长季土壤N2O排放量,且高氮处理还显著促进CO2排放和显著抑制CH4吸收,上述研究结果可为人工林缓释肥对土壤温室气体通量评估提供参数。 Abstract:Fertilization plays a vital role in maintaining the productivity of short-rotation plantations. Eucalyptus plantations are one of the fast-growing and high-yield plantations around the world and are numerous in south China. In order to improve nitrogen use efficiency, slow-release nitrogen fertilizers are being widely adopted. However, few studies have been done to assess the effect of slow-release fertilizer on the soil-atmosphere exchange of greenhouse gases (GHGs), such as carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). To clarify temporal changes of soil GHGs fluxes following slow-release N fertilizer application, field control trials with four levels of N application (Control: 0 kg/hm2; Low N: 84.2 kg/hm2; Medium N: 166.8 kg/hm2; High N: 333.7 kg/hm2) were initiated in a Eucalyptus plantation in Guangxi, southern China. At the beginning of growing season, the nitrogen fertilizer, urea formaldehyde (a kind of slow-release fertilizer), was applied according to the local fertilization practice (once a year). Static chamber and gas chromatography techniques were used to quantify soil GHGs exchange monthly during the study period from May to November 2013. Environmental factors, such as soil temperature at 5 cm depth and soil water content at 10 cm depth, were synchronously monitored while the GHGs were collected. Before N application, no significant differences were observed for soil GHGs fluxes in all N application treatments. The results showed that (1) CO2 emission fluxes, N2O emission fluxes, and CH4 absorption fluxes under four levels of nitrogen application were 276.84-342.84 mg m-2 h-1, 17.64-375.34 μg m-2 h-1 and 29.65-39.70 μg m-2 h-1, respectively. Fertilization resulted in a remarkable but short increase in soil respiration over the first 2 to 3 months during the observation period, and the differences in soil respiration between the High N treatment and the control treatment were significant. Nitrogen application significantly increased the N2O emission and persisted for 5 to 6 months after fertilization. Each N application treatment had a significant effect on N2O emission. Moreover, High N treatment had a significantly negative effect on CH4 oxidation. (2) During the growing season, CO2 emission had a significantly positive correlation with N2O emission (P < 0.01), and CH4 uptake had a significantly negative correlation with both CO2 emission and N2O emission (P < 0.05 and P < 0.01, respectively). With the increase of the amount of fertilizer, the CO2 emission fluxes increased and CH4 oxidation fluxes decreased,respectively. (3) Soil temperature and soil water content were the main factors influencing soil respiration, N2O emission, and CH4 oxidation. Soil temperature and soil water content had significantly positive effects on CO2 and N2O emission fluxes, and soil temperature had significantly negative effects on CH4 absorption fluxes. In conclusion, during the growing season in a Eucalyptus plantation, slow-release nitrogen application not only significantly in creases soil N2O emission, but also had significant effects on CO2 emission and CH4 oxidation after High N treatment. Our results can provide parameters for accurately assessing the effects of slow-release nitrogen application on GHGs fluxes in a Eucalyptus plantation. 参考文献 相似文献 引证文献

From California dreaming to California data: Challenging historic models for landfill CH4 emissions

Abstract Improved quantification of diverse CH4 sources at the urban scale is needed to guide local GHG mitigation strategies in the Anthropocene. Herein, we focus on landfill CH4 emissions in California, challenging the current IPCC methodology which focuses on a climate dependency for landfill CH4 generation (methanogenesis), but does not explicitly consider climate or soil dependencies for emissions. Relying on a comprehensive California landfill database, a field-validated process-based model for landfill CH4 emissions (CALMIM), and select field measurements at 10 California sites with a variety of methods, we support the contrary position: Limited climate dependency for methanogenesis, but strong climate dependency for landfill CH4 emissions. Contrary to the historic IPCC empirical model for methanogenesis with kinetic constants related to climate, we demonstrate a simpler and more robust linear empirical relationship (r2 = 0.85; n=128) between waste mass and landfill biogas recovery [126 × 10-6 Nm3 CH4 hr-1 Mgwaste-1]. More interestingly, there are no statistically significant relationships with climate, site age, or status (open/closed) for landfill biogas recovery. The current IPCC methodology does not consider soil or climate drivers for gaseous transport or seasonal methanotrophy in different cover soils. On the other hand, we illustrate strong climate and soil dependencies for landfill emissions—e.g., average intermediate cover emissions below 20 g CH4 m-2 d-1 when the site’s mean annual precipitation is &amp;gt;500 mm y-1. Thereby, for the California landfill CH4 inventory, the highest-emitting sites shift from landfills containing the largest mass of waste to sites dominated by intermediate cover types having a reduced rate of soil CH4 oxidation during the annual cycle. These differences have profound implications for developing more realistic, science-based urban and regional scale GHG inventories for landfill CH4 while reducing uncertainties for this important anthropogenic source.

Repeated fuel reduction burns have little long-term impact on soil greenhouse gas exchange in a dry sclerophyll eucalypt forest

Fuel reduction burning is a widespread management tool in fire-tolerant forest systems to mitigate wildfire risk, but has the potential to impact soil greenhouse gas exchange processes. Soil disturbance often alters soil carbon dioxide (CO2) and methane (CH4) flux; however, the influence of repeated fuel reduction burning upon these flux processes long-term is still not well understood. In this study we measure soil CH4 flux, soil methanotrophic activity and soil CO2 flux in all seasons from March 2009 to February 2011 in three different fire frequency treatments applied to a dry sclerophyll eucalypt forest (Victoria, Australia) for the last 27 years. The low-intensity fire treatments are forest burnt in autumn (i) every 3 years, (ii) every 10 years, and (iii) not burned (since before 1985). Mean soil CO2 emissions were greater in the burnt as compared to un-burnt treatments. In contrast, soil CH4 oxidation did not show a response to repeated burning and there was no statistical difference in soil CH4 flux among treatments. Furthermore, we did not detect changes in the relationships of soil CH4 flux or soil CO2 flux and key environmental controls. Our results indicate that low intensity fuel reduction burns have no cumulative negative impact on biogeochemical processes related to soil respiration or soil CH4 oxidation.

An analytical model for estimating the reduction of methane emission through landfill cover soils by methane oxidation

Landfill is an important source of atmospheric methane (CH4). In this study, the development and partial validation are presented for an analytical model for predicting the reduction of CH4 emission in landfill cover soils by CH4 oxidation. The model combines an analytic solution of a coupled oxygen (O2) and CH4 soil gas transport in landfill covers with a piecewise first-order aerobic biodegradation, including the influences of environmental factors such as cover soil thickness, CH4 oxidation and CH4 production rate. Comparison of soil gas concentration profiles with a soil column experiment is provided for a partial validation, and then this model is applied to predict the reduction of CH4 emission through landfill covers in several other cases. A discussion is provided to illustrate the roles of soil layer thickness, reaction rate constant for CH4 oxidation and CH4 production rate in determining CH4 emissions. The results suggest that the increase of cover soil thickness cannot always increase CH4 oxidation rates or removal efficiency, which becomes constant if the thickness of landfill cover soil is larger than a limit.

More evidence that anaerobic oxidation of methane is prevalent in soils: Is it time to upgrade our biogeochemical models?

Estimating future fluxes of CH4 between land and atmosphere requires well-conceived process-based biogeochemical models. Current models do not represent the anaerobic oxidation of methane (AOM) in land surface soils, in spite of increasing evidence that this process is widespread. Our objective was to determine whether AOM, or potential AOM, commonly occurs in 20 hydromorphic soils spanning a wide range of chemical properties. Bulk soil samples were collected under shallow water near the shoreline of 15 recently drained fish ponds in southern Bohemia (Czech Republic), as well as from below the water table at 3 peatland locations in northeast Scotland and 2 acid sulfate soils on the southern coast of Finland. Each soil slurry was incubated under both oxic and anoxic conditions, with or without the addition of alternative electron acceptors (SO42− and NO3−) or H2PO4−. Here, “oxic” and “anoxic” conditions refer to anoxic soil respectively incubated in a headspace containing air or argon. Using the isotope dilution method, we determined the gross production and oxidation rates of CH4 after 2 days incubation under oxic headspace conditions, and after 2, 21 and 60 days incubation under anoxic conditions. Large differences in net CH4 fluxes were observed between soil types and between incubation conditions. AOM was detected in each of the 20 bulk soil samples, which spanned >6 pH units and 2 orders of magnitude in organic C content. Significant positive relationships were found between AOM and gross CH4 production rates under anoxic conditions, resulting in AOM rates that were sometimes higher than CH4 oxidation rates under oxic headspace conditions. There was no relationship between net and gross CH4 production rates, such that 2 soil types could display similar low net rates, yet conceal very large differences in gross rates. The effects of alternative electron acceptors on AOM were idiosyncratic and resulted in no net trend. We did find, however, a negative effect of SO42− and H2PO4− on gross CH4 production rates under anoxic and oxic conditions respectively. Under oxic headspace conditions, CH4 oxidation was related to soil organic C content. Taken collectively, our results suggest that AOM, or potential AOM, is prevalent over a wide range of soil types, that AOM may contribute substantially to CH4 oxidation in soils, and that AOM in soils should be integrated to current process-based CH4 cycling models.